Antibiotics are medications designed to destroy or inhibit the growth of bacteria causing an infection. Probiotics are live microorganisms intended to confer a health benefit, typically by improving the balance of the gut flora.
A common concern is whether the antibiotic will nullify the effects of the probiotic when taken simultaneously. Understanding this interaction is important for maintaining gut health during treatment.
This guidance addresses the co-administration of probiotics and antibiotics, focusing on timing, dosage, and strain selection.
How Antibiotics Disrupt the Gut Microbiome
The primary mechanism of antibiotic action, while effective against pathogens, is often non-discriminatory toward the host’s existing microbial community. These medications destroy a wide range of bacteria, including the beneficial ones that naturally reside in the gut. This affects the intestinal flora, an intricate ecosystem essential for digestion, metabolism, and immune function.
The resulting disturbance is known as dysbiosis, characterized by a rapid drop in microbial diversity and a shift in community composition. Beneficial bacterial genera, such as Bifidobacterium and Faecalibacterium, are often depleted, allowing opportunistic microbes to proliferate. This imbalance compromises colonization resistance, the gut’s natural ability to suppress the growth of harmful invaders.
The Rationale for Continuing Probiotics
The decision to continue taking probiotics alongside antibiotics is based on mitigating the negative effects of dysbiosis. Introducing beneficial microorganisms during antibiotic therapy helps temporarily replace some lost flora, stabilizing the gut environment. This co-administration is a clinically supported strategy to reduce the risk of Antibiotic-Associated Diarrhea (AAD).
Clinical meta-analyses show that co-administration of probiotics can reduce the risk of AAD, with studies reporting a risk reduction between 37% and 55%. The introduced bacteria help restore microbial balance, minimizing the intestinal dysfunction that causes diarrhea. Probiotics also reinforce colonization resistance by competing with potential pathogens for nutrients and adhesion sites.
This strategy also addresses the overgrowth of Clostridioides difficile, a bacterium that can cause severe inflammation and colitis. Probiotics have shown a protective effect against C. difficile-associated diarrhea. By preserving microbial diversity, probiotics make the gut less hospitable to the toxins produced by this harmful organism.
Practical Protocol for Dosing and Timing
The answer to whether to stop taking probiotics is generally no; they should be continued throughout the antibiotic course. Successful co-administration requires precise timing to ensure the probiotic bacteria survive and reach the gut. Taking the probiotic too close to the antibiotic dose risks the medication destroying the live microorganisms.
A separation of at least two hours between the antibiotic and the probiotic is the standard recommendation to maximize the probiotic’s viability. This time gap allows the concentration of the antibiotic in the gastrointestinal tract to decrease, minimizing its impact on the newly ingested bacteria.
The recommended daily dosage, measured in Colony-Forming Units (CFUs), typically ranges between 5 billion and 40 billion CFUs per day for AAD prevention. Doses between 10 to 40 billion CFUs may be more effective for individuals at higher risk for digestive complications. It is recommended to continue the probiotic regimen for at least one to two weeks after the antibiotic course is completed to support the gut microbiome as it restores its natural balance.
Identifying Effective Probiotic Strains
The effectiveness of a probiotic depends highly on the specific strain chosen, as benefits cannot be generalized across all products. For mitigating AAD, certain strains have demonstrated reliable efficacy in clinical trials, emphasizing the importance of reading product labels carefully.
One of the most extensively studied and effective options is the yeast Saccharomyces boulardii. As a yeast, it is inherently resistant to antibacterial antibiotics, meaning it can be taken closer to the antibiotic dose, although the two-hour separation is still advised for safety. Specific bacterial strains that have shown efficacy include Lactobacillus rhamnosus GG (LGG) and Bifidobacterium animalis subsp. lactis.
The beneficial effects are strain-specific, meaning the proven efficacy of a strain like LGG does not extend to other Lactobacillus strains unless they have been individually tested. When selecting a product, look for those that explicitly list these clinically validated strains and a CFU count within the effective range. Choosing evidence-based strains increases the likelihood that the probiotic will provide targeted protection during antibiotic therapy.